DISRUPTION OF THE RELATIONSHIP BETWEEN FAT-CONTENT AND LEPTIN LEVELS WITH AGING IN HUMANS

Leptin released from adipose tissue is believed to participate in a ne gative feedback loop regulating appetite, and malfunction of this mech anism could lead to obesity. We measured plasma leptin and body compos ition (dual energy x-ray absorptiometry) in 70 healthy subjects, divid ed into 3 age groups (young, 25 +/- 1 yr; middle-aged, 53 +/- 1 yr; ol d, 70 +/- 1 yr), while on a 5-day weight-maintaining diet. Pairwise co rrelations were assessed using product-moment correlation, and regress ion analysis was used to evaluate relationships between leptin and oth er variables. Leptin concentrations and relative body fat content were correlated in young females (r = 0.71; P = 0.009) and in young males (r = 0.76; P = 0.007), but not in the combined middle-aged and elderly groups (r = 0.19; P = 0.36 and r = 0.19; P = 0.38 in females and male s, respectively). Regression analysis showed a clear correlation betwe en circulating leptin and relative fat mass in the young subjects (P = 0.0001), but not in the older subjects (P = 0.199). We conclude that body fat content in young subjects correlates with plasma leptin in bo th genders, whereas this relationship is disrupted in elderly subjects , thus possibly contributing to the obesity occurring with age.